1. Field of the Invention
The present invention relates to an optical recording medium capable of retaining the secrecy of stored information and to a method of erasing, recording, and reading the stored information while retaining a high level of secrecy.
2. Discussion of the Background
Optical recording media are disc-shaped media capable of being read and recorded to by optical devices. For example, Compact Discs (hereinafter referred to as CDs) such as a Compact Disc Digital Audio (CD-DA), a Compact Disc Read Only Memory (CD-ROM), a Compact Disc Recordable (CD-R), and a Compact Disc ReWritable (CD-RW), or large capacity optical recording media such as a Digital Video Disc Read Only Memory (DVD-ROM), a Digital Video Disc Recordable (DVD-R), and a Digital Video Disc ReWritable (DVD-RW) are well known. These media have become wide spread as information recording and transmitting media. In particular, CD-RW media have become remarkably wide spread as erasable/rewrite-able CD media.
When these optical media are used as information transmitting media, it is often important to keep information stored within the media secret. For example, data stored in a CD can be easily read by a commercially available CD drive or CD player. Therefore, a problem which occurs is that secret information is easily leaked when an optical recording medium used to store the secret information is read by an unauthorized person.
The CD-RW media can be reused by erasing information which has been stored. Information erasing methods for CD-RW include a full-erase method in which all the recorded data is erased and a quick-erase method in which only control data is erased. Control data is necessary to allow a CD drive to access the information stored in the data area of a CD-RW. The quick-erase method is used in order to quickly make a CD medium ready for rewriting.
FIGS. 4A and 4B are schematic diagrams illustrating area-structures of a CD-RW medium before and after information is erased by a quick-erase method, respectively. A prior art erase method is described hereinafter referring to FIGS. 4A and 4B.
In FIG. 4A, reference numerals 41, 42, 43, and 44 designate a program memory area 41 (hereinafter referred to as a PMA), a table of contents area 42 (hereinafter referred to as a TOC area), a program area 43, and a lead-out area 44, respectively.
User information is stored in the program area 43 of the CD-RW medium shown in FIG. 4A and a CD-RW drive gains access to the information in the program area 43 on the basis of control data recorded in the PMA 41. After the control data is additionally recorded in the TOC area 42 and the lead-out area 44, the information recorded in the CD-RW medium becomes capable of being read by a CD drive such as a CD-ROM drive. This recording operation is performed using a CD-RW drive.
When the described quick-erase method is used, all of the control data stored in the filing information areas, i.e., the PMA 41, the TOC area 42, and the lead-out area 44, are erased. The user information recorded in the program area 43 remain intact. However, there are no CD drives available which can read the user information stored in the program area 43, because there is no control data in the filing information areas.
Accordingly, there are currently no methods to read user information stored in the program area 43 of a CD-RW medium when the medium is accidentally erased by a quick-erase method.
The present invention has been made in view of the above-discussed problems and an object of the present invention is to address and solve these and other problems.
The present invention provides an optical recording medium which includes an information area. The information are is comprised of a data area, in which user information can be stored, and a filing information area, in which control data for access to the user information can be stored. Initially, the data area is in a recorded state and the filing information area is in an unrecorded state.
The optical recording medium may further include a password that is recorded in a portion of the information area.
The optical recording medium may be a CD-R or a CD-RW which includes an information area comprising a data area and a filing information area. The data area includes a program area in which user information is stored and a user area in which information can be stored. The filing information area contains control data used in accessing the stored user information. The filing information area includes a PMA, a TOC area, and a lead-out area. The user area, the TOC area, and the lead-out area are in an unrecorded state. Both the program area and a portion of the PMA are in a recorded state. The optical recording medium may further include a password that is recorded in a portion of the information area. When the medium is used as an information recording/reading system having system information that is peculiar to the system, the system information may be recorded in the medium. In this case, the system information is used as a password, and the verification of the password may be done by the information recording/reading system automatically. Specifically, when the system information is recorded in the data area, then control data for access to the system information may be further recorded in the PMA.
In another aspect of the present invention, an erase method for erasing CD-RW media is provided, which includes the steps of reading control data stored in a filing information area of a CD-RW medium, recording the control data in another medium, and erasing only the control data in the filing information area of the CD-RW medium.
In still another aspect of the present invention, an information recording/reading system is provided which includes an optical recording medium which includes a file information area. The file information area includes a PMA which is in an non-recorded state and a program area in which user information is stored; a control data storing medium which stores control data for access to the user information stored in the program area; and a recording device which records the control data in the PMA. The optical recording medium may be a CD-R medium or a CD-RW medium.